"Our customers love coupons and freebies, and they are giving us lots of great feedback and suggestions on our offers," said Nancy Smith, 7-Eleven's vice president of marketing. "We're always looking to deliver on our guests' wants and have partnered with MiO for this free offer as a result."

The offer will be available at participating stores while supplies last. No purchase is necessary, but customers must be 18 or older to participate.

MiO Energy Black Cherry Liquid Water Enhancer contains 60 milligrams of caffeine per serving -- the equivalent of a 6-ounce cup of regular coffee. The recommended serving size is one squeeze, about half a teaspoon, into an 8-ounce glass of water or two squeezes for a 16-ounce bottle of water.

As CSNews Online previously reported, bottled water is projected to see growth of 4.8 percent through 2015, making it a $125-billion industry.